In the image on the side you can appreciate various types of hymen.
This membrane - which more or less completely covers the outside of the vaginal opening - has in fact large morphological variations in the female population.
From the clinical point of view, the most important typology is that of the imperforate hymen, in which the membrane completely covers the vaginal opening.
It is a very rare condition, which requires a small surgical procedure, called "hymenectomy"; this intervention aims to create a small vaginal opening to allow the outflow of secretions and menstrual blood.
An imperforate hymen can create problems for the young woman, especially since the menarche, as it prevents menstrual blood from leaking out causing abdominal pain, primary amenorrhea, urinary retention, constipation and low back pain.